1. Field of the Invention
The present invention relates to an improved apparatus and process for the production of fried potato chips in batch-type kettles. In particular, the invention improves the efficiency of the production process by providing the ability to increase throughput and decrease fry time without diminishing the desired, characteristic "kettle-style" hardbite texture and taste of the finished product.
2. Description of the Background Art
Potato chips produced by batch processes in kettle fryers, known as kettle-style potato chips, have texture and flavor characteristics which are usually recognized by consumers as being distinctly different from typical commercially produced continuous process potato chips. Kettle fried chips are generally harder and crunchier than conventional potato chips produced in continuous fryers, and have a somewhat sweeter flavor that some consumers find more appealing than continuously fried commercial chips. In industry parlance, the hard, crunchy texture that is characteristic of kettle-fried chips is known as "hardbite" texture.
The dominant view among potato chip producers is that the batch frying method is what gives kettle-style chips their distinctive "hardbite" texture and characteristic flavor, although attempts have been made to produce kettle-style chips on a continuous basis. Van Wagner, L. R., Snack World, pp. 44-47, March 1989.
As the name implies, batch process kettle frying of potato chips involves placing a batch of potato slices in a kettle of hot oil (e.g., at 300.degree.-310.degree. F., about 150.degree.-160.degree. C.). Batch kettle frying of potato chips usually takes about 13 minutes to complete, during which the chips are manually stirred or raked. The need to stir or rake the chips places a constraint on the overall dimensions of the kettle fryer, as the operator must be able to reach all parts of the kettle. This constraint, in turn, limits fryer capacity as capacity is directly related to the surface area available for frying. Although mechanized stirrers are commercially available, size is still a limiting factor.
In the conventional kettle fryers used in the production of kettle-style chips, the cooking oil temperature follows a generally U-shaped time vs. temperature profile as follows. Upon introduction of the potato slices into the oil, the temperature of the oil typically drops quite rapidly by as much as 50.degree. F. (about 28.degree. C.) or more, and then the temperature of the oil begins to gradually rise, reaching about the initial frying temperature at the bubble end point of the chips (about 2% moisture content by weight or less). It is believed in the art that this temperature profile imparts the intense flavor and unique mouth feel characteristic of kettle-style chips. This belief is largely empirical, however, as the commercially-available kettle fryers are relatively unsophisticated equipment that are significantly constrained by burner capacity and heat transfer capacity. Thus, the observed U-shaped time/temperature profile is unavoidable with the conventional equipment, as the system cannot supply heat quickly enough to overcome the large heat sink created by the addition of a batch of raw potato slices. Changes in oil volume, initial fry temperature or potato batch weight will cause changes in temperature profile and finished product attributes. Therefore, the production of potato chips having the desired kettle-style attributes requires the adjustment of the process parameters in a manner which results in the U-shaped time/temperature profile.
Production rates using batch kettle fryers are dependent upon the equipment used. The modern kettles that are utilized in batch processes are generally manufactured of stainless steel, and vary in size and capacity. The kettles typically are heated by gas burners positioned directly under the kettle floor. Fryer capacities range from as few as 60 pounds per hour to up to 300 pounds per hour, although most batch fry operations have kettle fryers that can manufacture between 125 and 200 pounds of chips per hour. In order to efficiently use a batch kettle fryer of a given size, it is necessary to maintain a particular "load " or amount of potato slices per volume of oil, in order to produce the desired U-shaped time/temperature profile. These and other constraints provide limits on the amount of throughput using batch kettle fryers.
There remains a need in the art for improvements in the production of kettle-fried potato chips. Specifically, there remains a need for increasing the production rate and production efficiency of kettle-fried potato chips without diminishing the desired hardbite texture and flavor.